A068647
Primes in which a string of 6's is sandwiched between two 1's.
Original entry on oeis.org
11, 16661, 1666666666661, 16666666666666661, 1666666666666666661, 1666666666666666666666666666666666661, 16666666666666666666666666666666666666666666666666661
Offset: 1
11 is also a member in which a string of 0 6's is there between two one's.
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Select[Table[10*FromDigits[PadRight[{1},n,6]]+1,{n,60}],PrimeQ] (* Harvey P. Dale, Jun 18 2021 *)
A156166
Numbers k > 0 such that (10^(k+2) + 666)*10^k + 1 is prime.
Original entry on oeis.org
1, 14, 43, 507, 609, 2473, 2624, 28292, 181299
Offset: 1
Cf.
A082700 and search results for 16661.
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[n: n in [1..500] | IsPrime((10^(n+2)+666)*10^n+1)]; // Vincenzo Librandi, Nov 15 2014
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A156166:=n->`if`(isprime((10^(n+2)+666)*10^n+1), n, NULL): seq(A156166(n), n=1..10^3); # Wesley Ivan Hurt, Nov 16 2014
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Select[Range[10^3], PrimeQ[(10^(# + 2) + 666)*10^# + 1] &] (* Arkadiusz Wesolowski, Sep 08 2011 *)
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for( n=1,9999, ispseudoprime((10^(n+2)+666)*10^n+1) & print1(n","))
A056247
Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) + 51 for n > 0.
Original entry on oeis.org
0, 3, 11, 15, 17, 35, 51, 71, 99, 6231, 24027, 40221, 66393
Offset: 1
16661 is prime, hence 3 is a term.
- Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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Select[Range[0, 2000], PrimeQ[(150 10^# - 51) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
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a=11;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+51)
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for(n=0,1500,if(isprime((150*10^n-51)/9),print1(n,",")))
Additional comments from
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Added one more term from the PDP table and a link, by
Patrick De Geest, Nov 02 2014
Showing 1-3 of 3 results.
Comments